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% Context Diagram
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\subsection{Context diagram}

The context diagram for the SAB System is shown in figure \ref{fig:Context}. The diagram illustrates how the system communicates with external components. A one-to-one mapping can be observed, this is the result of proper encapsulation of communication endpoints.

The system interacts with SWIFT for both interbank transactions and POS terminal payments. We need to be able to process POS terminal instructions and respond to them timely. We wish to both send out and receive interbank transaction credits, which use an asynchronous status update protocol. This requires both parties to expose an interface.

SAB cooperates with Atos Worldline to provide bank card related services. However, the system only needs to contact Atos Worldline directly to request new bank cards and to block existing ones. This requires them to expose an interface. Bank card payments happen either with the POS Terminal through SWIFT or at the ATM Terminal.

SAB outsources fraud detection to a third party company. The system sends out transaction histories and the company sends the results back a certain time later. This asynchronous communication requires both parties to expose an interface.

The other interactions shown in the diagram (i.e. with the direct debit beneficiary, with the employee for the \emph{Employee Web App}, with the customer for \emph{SAB Online} and with the ATM terminal) are services offered by the SAB system. SAB exposes an interface for each of these. 

\begin{figure}[!ht]
    \centering
        \includegraphics[width=0.8\textwidth]{images/Context.png}
    \caption{Architectural context diagram.}
    \label{fig:Context}
\end{figure}